1. Field of the Invention
The present invention relates to a method of manufacturing a thin metal film with an embossed pattern formed thereon to be used as a pigment material for holograms.
2. Description of the Related Art
Thin metal films having embossed pattern has conventionally been known as a pigment material for hologram. Such a thin metal film has an embossed surface which forms a pattern thereon, as shown in FIG. 4, to produce a superior iridescent effect through diffraction and interference of incoming light. Hologram pigments using such a thin metal film show stronger interference colors than conventional pigments made of, for example, mica, as shown in FIG. 5.
A typical method for manufacturing such a thin metal film with embossed pattern is disclosed in Japanese Patent Laid-Open Publication No. Hei 6-24199, in which the embossed pattern is first transferred to a thermoplastic resin and a thin metal film is deposited on the surface where the embossed pattern is transferred.
Thermoplastic resin is therefore required in such conventional methods. Because of this, it is difficult to precisely transfer the embossed pattern by pressing the embossed pattern formed on a die against the thermoplastic resin, because the resin is usually a relatively soft material. Also, because of the high temperature of the thermoplastic resin heated while manufacturing the thin metal film with embossed pattern, deformation or lose of the embossed pattern that has been transferred to the thermoplastic resin is not uncommon.
For these reasons, superior interference colors cannot be obtained by the thin metal film with embossed pattern which is fabricated using thermoplastic resin.
The present invention is made to solve the above-described problems and provides a method for manufacturing a thin metal film with embossed pattern which is capable of precisely receiving the embossed pattern and delivers a strong interference color.
The above object is achieved by a method for manufacturing a thin metal film with embossed pattern according to the present invention which includes steps of pressing an embossed original plate against a thermosetting resin, heat curing the thermosetting resin, peeling off the embossed original plate from the thermosetting resin, and forming a thin metal film on the embossed surface of the thermosetting resin.
Alternatively, the present invention provides a method for manufacturing a thin metal film with an embossed pattern including steps of applying a thermosetting resin to an embossed original plate, heat curing the thermosetting resin, applying to the thermosetting resin a second resin having high affinity with the thermosetting resin, binding the resins together, peeling off the embossed original plate from the thermosetting resin bonded to the high affinity resin, and forming a thin metal film on the embossed surface of the thermosetting resin.
It is a feature of the present invention that a coating containing a hydrocarbon group is applied to the surface of the embossed original plate prior to applying the thermosetting resin.
The hydrocarbon group is methyl, phenyl, hexyl, or decyl; the resin having high affinity with the thermosetting resin is polyvinylalcohol; and the thermosetting resin is a silicon or acrylic crosslinking resin.
It is another feature of the present invention that the step of heating and curing the thermosetting resin is carried out by heating the thermosetting resin until it is half-cured.
Alternatively, the present invention provides a method for manufacturing a thin metal film with an embossed pattern including steps of pressing an embossed surface of a heated die against a thermosetting resin while it is being cured, removing the die from the thermosetting resin, and forming a thin metal film on the embossed surface of the thermosetting resin.
It is a feature of the present invention that the die is a transfer roller having an embossed pattern formed on its surface.
Therefore, the present invention can ensure that the embossed pattern is precisely transferred by drying and curing the thermosetting resin on the embossed original plate before peeling off the resin from the original plate.
In addition, it is possible to peel off the thermosetting resin easily from the embossing belt, because the thermosetting resin is adhered to a resin having high affinity with the thermosetting resin.
It is also possible to further ensure the precise transfer of the embossed pattern, because the thermosetting resin is hardened while the embossed original plate is pressed against the resin.